Twenty eight Indians have been recently detained after being found working illegally at the construction site of Pembroke Power Station by the UK Border Agency.
The enforcement operation was carried out as part of a UK-wide campaign to tackle immigration crime and was the largest raid carried out by the agency in Wales this year.
After receiving information that suspected illegal workers were being employed by a building sub-contractor, officers from the agency, supported by Dyfed-Powys Police, went to the power station early on Thursday and checked the immigration status of workers. Sources said a majority of them were Punjabis.
Julian Smith, who heads the UK Border Agency's South West Wales local immigration team, said that 28 Indians were found to have no legal right to work in the UK. "They had committed a range of immigration offences including staying in the UK after their visas expired, entering the UK illegally and working in breach of their visa conditions," he added.
While 11 accused would remain in immigration detention pending deportation, one man has been arrested by Dyfed-Powys Police on suspicion of using a false identity document and 16 have been placed on immigration bail. The men must report weekly to a police station while the UK Border Agency secured the emergency travel documents necessary to deport them.
Building sub-contractor Sisk has been served with a civil penalty notice for employing illegal workers. If the employer is unable to prove to the agency that right-to-work checks were carried out before giving the men jobs, a fine of up to £10,000 will be imposed for each worker.
Smith said: "It was by far the biggest illegal working operation in Wales this year. I hope this sends out a message to other employers about need to ensure your staff are entitled to work in the UK. We don't expect employers to be experts at detecting forgeries - that's our job - but there is a legal obligation to carry out basic checks during the recruitment process."
Immigration Minister Damian Green said: "This operation is among many being carried out across the country following the success of a major crackdown on immigration crime during the summer, which generated a large number of arrests, cash seizures and prosecutions as well as fresh intelligence."
"Together with the police and the serious organised crime agency we will continue to make life as difficult as possible for those who cheat the immigration system," Green said.
Since July more than 400 operations have taken place across the UK resulting in over 800 arrests and over £500,000 cash seized under the Proceeds of Crime Act (POCA).